JP2002082563A - Fixing device and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent wear of a fixing roll while maintaining peeling performance in a fixing device for fixing a toner image on a recording medium by making a recording medium carrying an unfixed toner image pass through a nip part formed by a pair of rolls and heating and pressurizing. SOLUTION: This fixing device is equipped with a peeling assist member 67 assisting to peel the recording medium P passing through the nip part 63 from the fixing roll 61, and the member 67 is a blade-shaped one spread all over the passing area of the recording medium in the rotary shaft direction of the roll 61. Assuming that a gap between the member 67 and the roll 61 is (g) and the width in a carrying direction in a non-image area on the recording medium is (d), the member 67 is disposed at a position satisfying d×0.25>=g just behind the nip part in the carrying direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device and an image forming apparatus such as a printer, a facsimile, a copying machine, etc. having the fixing device, and more particularly, to a nip portion formed by a pair of rolls or a roll and a belt. The present invention relates to a fixing device that passes a recording medium carrying an unfixed toner image through a nip portion to be formed, heats and presses the recording medium to fix the toner image on the recording medium, and an image forming apparatus including the fixing device.

[0002]

2. Description of the Related Art An image forming apparatus using an electrophotographic process, such as a printer, a facsimile, and a copying machine, has a fixing device for fixing a toner image transferred onto a sheet or the like to the sheet.

The fixing device includes a fixing roll that rotates with a heat source, a predetermined nip portion formed by pressing the fixing roll, and a rotating pressure roll or a moving belt. A configuration is often used in which a sheet carrying paper is passed through the nip portion, heated and pressed to melt the toner and permeate the sheet to fix the toner image.

[0004] Ideally, paper that has passed through the nip is discharged without being wound around any roll or belt. The amount of toner is not uniform. Therefore, it is difficult to discharge the paper or the like without winding it on any roll or belt under all conditions.

Therefore, it is necessary to provide a separation assisting member downstream of the roll from the nip so that the paper or the like that has passed through the nip is not wound around the roll or belt even when used under various conditions.

Conventionally, as the peeling assisting member, a peeling claw is generally provided in some places in the rotation axis direction of the fixing roll. However, the roll is worn out or a jam occurs by providing the peeling claw. There is a problem.

In order to solve this problem, Japanese Patent Laid-Open Publication No.
Japanese Patent Application Laid-Open No. 7178 discloses that the peeling nail is partially in non-contact.

[0008]

However, even if such a peeling claw is partially non-contacted, it is still not possible to prevent abrasion, and if it is not contacted, the peeling performance is reduced. .

SUMMARY OF THE INVENTION In view of the above circumstances, an object of the present invention is to provide a fixing device having a configuration in which abrasion of a fixing roll is prevented while maintaining a peeling performance, and an image forming apparatus provided with such a fixing device. And

[0010]

A fixing device according to the present invention, which achieves the above object, comprises a fixing roll which rotates by forming a nip portion in contact with a predetermined contact member, and the nip portion is provided in the nip portion. In a fixing device that heats and pressurizes a recording medium that carries the unfixed toner image carried on the fixing roll side and fixes the unfixed toner image to the recording medium, the recording medium includes the recording medium. The fixing device has a non-image area which is guaranteed not to carry an unfixed toner image over a predetermined width in the conveyance direction at a front end portion of the medium in the conveyance direction. The fixing device further includes a peeling assisting member for assisting peeling from the fixing roll, and the peeling assisting member is a blade-shaped member that extends over the entire area where the recording medium passes in the rotation axis direction of the fixing roll. And, when the gap between the separation auxiliary member and the fixing roll is g, and the width of the non-image area on the recording medium in the conveyance direction is d, the separation auxiliary member is located immediately after the nip portion with respect to the conveyance direction. It is characterized by being arranged at a position satisfying d × 0.25 ≧ g.

Here, it is preferable that the side of the peeling auxiliary member on the fixing roll side of the peeling auxiliary member is disposed closer to the fixing roll than the contact member.

According to another aspect of the image forming apparatus of the present invention, a toner image is formed on a predetermined image carrier, and the toner image is finally transferred onto a predetermined recording medium. In the image forming apparatus for forming an image composed of a fixed toner image on the recording medium by conveying the recording medium onto which the image has been transferred to a fixing device and heating and pressing the recording medium, the recording medium is transported by the recording medium. A non-image area, which is guaranteed not to carry an unfixed toner image over a predetermined width in the transport direction, at the front end in the direction, and the fixing device has come into contact with a predetermined contact member. A fixing roll that forms and rotates a nip portion; and a separation assisting member that assists in separating the recording medium that has passed through the nip portion from the fixing roll. It is a blade-like member that spreads over the entire passing area of the recording medium in the rotation axis direction, and the gap between the separation assisting member and the fixing roll is g, and the width of the non-image area on the recording medium in the transport direction is d. In this case, the peeling assisting member is provided at a position that satisfies d × 0.25 ≧ g immediately after the nip portion in the transport direction.

[0013]

Embodiments of the present invention will be described below.

FIG. 1 is a schematic configuration diagram showing an embodiment of the image forming apparatus of the present invention.

The image forming apparatus 10 includes a photoreceptor 1 rotating in the direction of arrow A, a scorotron charging device 2 for charging the surface of the photoreceptor 1, and an exposure in which the surface of the charged photoreceptor 1 is modulated by image information. ROS (laser output unit) 3 that forms an electrostatic latent image on photoconductor 1 by exposing with light R, and forms a toner image on photoconductor 1 by developing the electrostatic latent image on photoconductor 1 with toner Developing device 4, transfer device 5 for transferring the toner image on photoconductor 1 to paper P, fixing device 6 for fixing the toner image transferred to paper P, paper tray 7 for storing paper P, photoconductor 1 Cleaner 8 for cleaning the surface, photoconductor 1
A static eliminator 9 for removing residual charges on the surface is provided.

Next, an image forming operation in the image forming apparatus will be described with reference to FIG.

First, an original image signal read from a document by an image reading unit (not shown) or an original image signal created by an external computer (not shown) is sent to an image processing unit (not shown). Input and appropriate image processing is performed.
The input image signal thus obtained is input to the ROS (laser output unit) 3 and modulates the laser beam R. The laser beam R modulated by the input image signal is raster-irradiated onto the surface of the photoconductor 1 uniformly charged by the scorotron charging device 2. When the surface of the photoconductor 1 is irradiated with the laser beam R in a raster, an electrostatic latent image corresponding to the input image signal is formed on the photoconductor 1.

The electrostatic latent image formed on the photoconductor 1 is developed with toner by the developing device 4 to form a toner image on the photoconductor 1. The toner image formed on the photoconductor 1 is conveyed toward a transfer device 5 arranged opposite to the photoconductor 1 as the photoconductor 1 rotates in the direction of arrow A.

On the other hand, the paper P stored in the paper tray 7 is supplied toward a nip portion between the photoconductor 1 and the transfer device 5, and the toner image on the photoconductor 1 is transferred onto the paper P by the transfer device 5. Is transferred to The toner image transferred onto the sheet P is conveyed and fixed by the fixing device 6 to obtain a desired image.

After the transfer of the toner image onto the paper P is completed, the deposits such as residual toner adhered to the surface of the photoreceptor 1 are cleaned by the cleaner 8, and the residual charges on the surface of the photoreceptor 1 are removed by the charge removing device 9. And one image forming operation is completed.

FIG. 2 is a configuration diagram of the fixing device 6 employed in the image forming apparatus 10 shown in FIG. The fixing device shown in FIG. 2 also corresponds to an embodiment of the fixing device of the present invention.

The fixing device 6 includes a fixing roll 61 rotating in an arrow X direction and an opposing roll 6 rotating in an arrow Y direction.
2 which are in contact with each other to form a nip 63.

The fixing roll 61 has a cylindrical core 611.
And a release layer 613 formed of a resin material and covering an elastic layer 612 covering the metal core 611 and a surface of the elastic layer.
The heating is performed by a heat source 64 disposed inside the cored bar 611.

A temperature detecting device 65 for detecting the temperature of the surface of the fixing roll 61 is provided around the fixing roll 61, and the temperature of the fixing roll 61 is not shown so as to be a predetermined temperature. Heat source 6 via control unit
4 is controlled.

Further, in the vicinity of the fixing roll 61,
A peeling guide 67 for peeling the paper P coming out of the nip 63 from the fixing roll 61 is provided. The peeling guide 67 moves in the rotation axis direction of the fixing roll 61 (FIG. 2).
(In the direction perpendicular to the plane of the drawing), the blade P extends over the entire area where the sheet P passes. The peeling guide 67 may be an integrated product or a plurality of separated products.

The sheet P to which the toner image T has been transferred by the operation of the transfer device 5 shown in FIG.
Is heated in the nip portion 63 sandwiched between the fixing roll 61 and the pressing roll 62 and is pressurized, and the release layer 61 on the surface of the fixing roll 61.
3 and the fixing roll 61 by the action of the peeling guide 67.
And is discharged to the outside of the image forming apparatus 10 shown in FIG. An image composed of a toner image fixed by heating and pressing in the fixing device 6 is formed on the discharged sheet P.

FIG. 3 is an enlarged view of a part of the fixing device shown in FIG.

Here, the width dimension w of the nip 63 in the paper transport direction and the dimension g of the gap between the peeling guide 67 and the fixing roll 61 are shown.

Here, as shown in FIG. 2, the sheet P is placed on the leading end of the sheet P in the conveying direction (the direction of arrow A shown in FIG. 2) by the operation of the image forming apparatus 10 shown in FIG. The separation guide 67 has a region R that is guaranteed not to carry an unfixed toner image over the width d in the transport direction, and the peeling guide 67 is provided with d × 0.25 ≧ g immediately after the nip portion 63 in the transport direction. (1) and the peeling guide 67
The side 67 a on the side of the fixing roll is disposed closer to the fixing roll 61 than the pressing roll 62.

Table 1 shows the distance d (see FIG. 2) in the transport direction of the non-image area R at the leading end of the sheet P and the leading end a of the peeling guide 67.
4 is a table showing the peeling performance when the position g (see FIG. 3) is variously changed.

[0031]

[Table 1]

From this table, it can be seen that sufficient peeling performance can be obtained by arranging the peeling guide 67 at a position satisfying the above expression (1). Further, since the peeling guide 67 is arranged at a position separated from the fixing roll 61, it is possible to prevent the fixing roll 61 from being damaged by the peeling guide 67.

Table 2 shows the state of the fixing roll (particularly, the state of the release layer) when 100,000 sheets of paper P are passed through the fixing device 6 shown in FIG.

[0034]

[Table 2]

As shown in FIG. 2, the fixing roll 61 and the pressure roll 62 are in contact with each other to form a nip 63, where the roll is deformed and the surface speed of the roll is reduced. Only 63 are different. If the speed difference (%) between the surface speed of the fixing roll 61 in a portion other than the nip portion and the speed in the nip portion (this speed is also the sheet conveyance speed when sandwiched between the nip portions) is large, To that extent, the paper P after passing through the nip portion 63 is easily peeled off from the fixing roll 61.

Table 2 shows the state of the fixing roll with respect to the speed difference (%) after 100,000 sheets have passed.

It can be seen from Table 2 that no problem occurs in both the elastic layer 612 and the release layer 613 of the fixing roll 61 at a speed difference of 2%. When the speed difference was 4%, wrinkles occurred in the release layer 613, but this was not at a level that would affect the image, and there was no problem. When the speed difference was 6%, a slight image defect occurred, and when the speed difference was 7%, the degree of the image defect became severe.

As described above, by giving a speed difference of 4% or less, the peeling of the paper from the fixing roll becomes much easier without causing a problem in the image when 1,000,000 sheets are passed.

Here, the fixing device in which the nip portion is formed by the fixing roll and the pressure roll has been described, but a belt-shaped member is provided instead of the pressure roll, and the fixing roll and the belt-shaped member are provided. A fixing device in which a nip portion is formed by the above method may be employed.

Although the description has been made of the configuration in which the oil application mechanism is eliminated, an oil application mechanism may be provided.

Although the image forming apparatus of the type in which the toner image formed on the photosensitive member is directly transferred onto the sheet P has been described, the present invention relates to a method for forming the toner image formed on the photosensitive member. The present invention can also be applied to an image forming apparatus of a type in which the toner image is transferred to an intermediate transfer body once and the toner image transferred on the intermediate transfer body is transferred to a sheet. The present invention can be applied to an image forming apparatus of a type that forms an image.

[0042]

As described above, according to the present invention,
Sufficient peeling performance can be provided without damaging the fixing roll.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram illustrating an embodiment of an image forming apparatus of the present invention.

FIG. 2 is a configuration diagram of a fixing device employed in the image forming apparatus shown in FIG.

3 is an enlarged view of a part of the fixing device shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photoreceptor 2 Scorotron charging device 3 ROS (laser output part) 4 Developing device 5 Transfer device 6 Fixing device 7 Paper tray 8 Cleaner 9 Static eliminator 10 Image forming device 61 Fixing roll 62 Opposing roll 63 Nip portion 64 Heat source P Paper R Exposure light

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Ryuichi Inamiya 2274 Hongo, Ebina-shi, Kanagawa Prefecture Fuji Xerox Co., Ltd. In-house (72) Inventor Yasutaka Naito 2274 Hongo, Ebina-shi, Kanagawa Prefecture Fuji Xerox Co., Ltd. Ebina Office F-term (reference) 2H033 AA16 AA26 BA16 BA19 BA20 BA21 BB01 BB28

Claims (3)

[Claims] An image forming apparatus comprising: a fixing roll configured to rotate while forming a nip portion in contact with a predetermined contact member; and an unfixed toner image conveyed to the nip portion is carried on the fixing roll side. In a fixing device that heats and presses a recording medium to fix the unfixed toner image on the recording medium, the recording medium is unfixed at a leading end of the recording medium in a conveyance direction over a predetermined width in the conveyance direction. The fixing device has a non-image area that is guaranteed not to carry a toner image, and the fixing device includes a separation assisting member that assists separation of the recording medium that has passed through the nip portion from the fixing roll, The separation assisting member is a blade-shaped member that extends over the entire area where the recording medium passes in the rotation axis direction of the fixing roll, and a gap between the separation assisting member and the fixing roll. When the gap is g and the width of the non-image area on the recording medium in the transport direction is d, the separation assisting member satisfies d × 0.25 ≧ g immediately after the nip portion in the transport direction. A fixing device, wherein the fixing device is disposed at a position where the fixing device is positioned. 2. The fixing device according to claim 1, wherein the separation assisting member is arranged such that a side of the separation assisting member on a fixing roll side is closer to the fixing roll than the contact member. . 3. A toner image is formed on a predetermined image carrier, the toner image is finally transferred onto a predetermined recording medium, and the recording medium with the transferred toner image is conveyed to a fixing device. An image forming apparatus that forms an image composed of a fixed toner image on the recording medium by heating and pressurizing the recording medium, wherein the recording medium is provided at a leading end in a conveying direction of the recording medium over a predetermined width in the conveying direction. The fixing device has a non-image area that is guaranteed not to carry a toner image, wherein the fixing device forms a nip portion that is in mutual contact with a predetermined contact member, and rotates with a fixing roll. A peeling assisting member for assisting the peeling of the recording medium that has passed through the nip portion from the fixing roll, the peeling assisting member being disposed in the entire area of the recording medium passing area in the rotation axis direction of the fixing roll. When the gap between the auxiliary separating member and the fixing roll is g, and the width of the non-image area on the recording medium in the transport direction is d, the auxiliary separating member is The image forming apparatus is provided at a position that satisfies d × 0.25 ≧ g immediately after the nip in the transport direction.